[en] Three winter wheat growing seasons were compared in order to analyse crop development, CO2 fluxes
and inter-annual variability in productivity. Crop development monitoring, leaf scale measurements
and continuous eddy-covariance measurements were conducted in a production crop at the Lonzée
experimental site in Belgium. The 3 years were characterised by similar soil proprieties (same site),
similar management (sowing, harvesting, plant protection and nitrogen application, adhering to regional
standards), and the use of recommended cultivars (the most productive ones for this region).
The comparison of carbon fluxes, growth and productivity in the three growing seasons highlighted
mechanisms affected by meteorological conditions and, in some cases, modulated by a cultivar effect. In
particular, it was shown that (a) precociousness or lateness in stage development was triggered mainly
by cumulated temperature during winter and early spring; (b) early development in one season could
explain the larger ecosystem net carbon sequestration that year, but had no impact on grain yield; (c)
low grain yield in one season was the result of a complex mechanism including drought in early spring,
which hindered flag leaf development, and moist conditions in late spring, which restrained radiation
and favoured the development of fungal diseases.
In all cases, it was found that grain yield could not be related to gross primary productivity or net
ecosystem exchange, suggesting that reallocation and translocation processes play a substantial role in
grain filling.